I read a lot of reviews on the SPD Adapters and it seems like more people didn't notice any gains vs. those who did notice gains (just like with Cold Air Intakes). Hopefully the Factory Tune will be the best for your upgrade. Looks good... I would have done the SVC's but at the time RPG was the only thing not he market and I have been happy with them. Wish they had a 2.5" RPG back when I got my truck.